Another thought on coolant flow

[ndutton]

As relayed to me by Tom Thatcher (Thatch), he's best to describe the details but I'll start the ball rolling.

Tom reasoned that with the backward tilt virtually all of us have, coolant entering the high point of the manifold would immediately and naturally move in a downhill direction, that is, away from the UHS (Ubiquitous Hot Spot). He did not suggest this was the reason for the hot spot, I mentioned the UHS as a position reference (although . . . . hmmm, I wonder, given our informal poll a while back that showed more tilt almost guaranteed the hot spot, by like 90%).

He explained that if coolant was introduced at the lower end, the manifold would have to fill completely without voids before it could exit at the higher end, the opposite of how our engines are normally plumbed.

It made a Helluva lot of sense to me. Check out his pics.






I should also mention that after bench testing for flow, he found cast plumbing elbows performed dramatically better than those pretty machined ones.

[Mo]

Pretty sharp.

[hanleyclifford]

Interestingly the manifold failure I experienced was at exactly that spot. I wonder how many such failures might be related to this UHS. This could be a breakthru. Nice job, Tom!

[Administrator]

cast plumbing elbows performed dramatically better than those pretty machined ones

In what respect?

Bill

[Administrator]

Typically, the cold stuff and the hot stuff in a heat exchanger flow in opposite directions ("countercurrent flow"). Does this idea violate that principle?

Is the heat exchanger fill cap above the manifold?

Bill

[ndutton]

We'll need Tom to provide the details but as I understand it, his test setup measured flow using the same pump with the two different styles of elbows.

[ndutton]

Typically, the cold stuff and the hot stuff in a heat exchanger flow in opposite directions ("countercurrent flow"). Does this idea violate that principle?

If you're referring to the jacketed manifold, I can see where Tom's plumbing scheme supports the countercurrent principle whereas the standard plumbing does not (exhaust and coolant outlet at the same end).

[Administrator]

I can see where Tom's plumbing scheme supports the countercurrent principle whereas the standard plumbing does not (exhaust and coolant outlet at the same end).

Hmmm. That's very interesting. I don't know that I'd want to tinker with something so fundamental after all these years of field experience, but if I were a young engineer sitting in a design review meeting as the concept was being developed, I'd be asking a bunch of questions.

Bill

[hanleyclifford]

But Bill, this IS a design review meeting/forum. Tom's idea needs to tested some more and I intend to do just that on my engine. Hanley

[ndutton]

Anybody see any problems with the reversed waterjacket flow?

I'll go first. I don't. The whole concept intrigued me and I don't think the manifold casting cares where the coolant enters and exits. Add the tilt factor and gravity (and the UHS) and it looks like it could be a real improvement.

I'm starting to amass the parts for FWC now that electric coolant pumps are surfacing and I'm really thinking of doing the described replumb as part of the project. I'd like to hear of any, ANY reason not to.

I'll throw it in here rather than another thread, Tom also has an excellent pic of his electric coolant pump installation.

[hanleyclifford]

going to antifreeze cooling

Neil - Because you will be reversing the flow in a manifold used for raw water cooling there could be an issue with dislodging metal flakes and chips. May I suggest that you remove the freeze/casting plugs and thread the holes for 3/4"NPT brass plugs. I did this and was able to accomplish a very thorough cleaning. In addition, the threaded holes give future access and can be used for temp monitoring. Hanley

[ndutton]

Agreed. After 33 years of RWC, the move to FWC will certainly include a thorough descaling throughout.

Here are a couple low-res pics of the HX I bought this week. The journey begins . . .

[hanleyclifford]

That is one rugged looking unit - stainless and copper?. It will be interesting to see how you design the fill and header tank. Keep us posted.

[Dave Neptune]

2 cents and 2 cents.

I like the idea (Tom's) about the filling of the manifold from the low end it makes sence. I'm not sure that it will eliminate the hot spot as the manifold is a symetric casting. Some are drilled for the exhaust to exit the front of the engine so there is no water jacket around the area that is exposed to the exhaust. I believe the hot spot is normal and nothing to worry about. However the water filling from the bottom will elimanate the air pocket that could form and not go away.

I have a lot of experience in low preassure hudraulics and the cast fitting do flow much better. I always "port them a bit if there is a bit of a casting lump on the mael ends. They flow better because they turn the flow in a radiused orfice. The machined fitting have the flow crash into a wall where it bounces around and finds relief and begins to head in the new direction. They many times appear more open but don't flow as well.

I have also been involved in testing oil cooler performance on offshore racers wit some awsome "thunder motors" well in excess of a 1000 HP. One interesting point is that the coolers performance was affected by the direction it was facing and the angle it was mounted. If we moved the water aft and the oil forward with the water coming in at the low end worked best. I don't remember how mch cooler they ran but we changed many instalations after finding that out with a heat gun and guages.

I have a raw water motor that is 40 years old and does not lend itself to an extra pump. I am seriously thinking of going the the electric and going to a HX.

How much current does the pump draw?

Dave Neptune

[ndutton]

I have a raw water motor that is 40 years old and does not lend itself to an extra pump. I am seriously thinking of going the the electric and going to a HX.

How much current does the pump draw?

As I recall from the Johnson specs, 2 amps.

edit: Oops, my mistake. It's fused at 1.6 amps
reference:

http://www.johnsonmarinepumps.com/specialty_pumps/Circulating_Pumps/cm10p7_1.jpg